The long-term objective is elucidation of the chemical mechanism of neurotransmitter receptor-mediated reactions in the membrane of nerve and muscle cells. Techniques developed by this group enable one to study elementary steps of the reactions, information needed to understand the regulation of signal transmission between the approximately 10(12) cells in the human nervous system. Specific aims are to: 1. Determine reaction mechanisms of excitatory acetylcholine and glutamate and inhibitory GABA and glycine receptors. The knowledge gained is required to account for the integration of excitatory and inhibitory signals by a single cell. 2. Understand the modification of receptor function by therapeutic agents, abused drugs, and combinatorially synthesized RNA polymers. Receptors in cells and genetically engineered forms expressed in X. laevis oocytes will be used to understand how these compounds affect receptor mechanisms. 3. Understand the integrated action of a known circuit of neurons controlling a measurable behavioral response, pharyngeal pumping, in the nematode C elegans. Neurotransmitters secreted by specific cells and responding receptors in target cells will be identified. Health Relatedness of the Project: Neurotransmitter receptors regulate intercellular communication in the central nervous system and provide the mechanism by which environmental information is received, stored, and transmitted. They are implicated in nervous system diseases (Alzheimer's, Parkinson's) and are the targets of therapeutic agents (for instance, Prozac(TM), tranquilizers) and abused drugs. Understanding how receptor-mediated reaction mechanisms are modified is required for rational clinical treatment of diseases and the design of improved drugs. Research Design: Rapid reaction techniques, newly developed by this group and suitable for studying reactions on cell surfaces in the mu s-ms time region, will be used. Receptors are equilibrated with a photolabile, biologically inert neurotransmitter precursor before photolysis releases the neurotransmitter in mu s, thereby initiating the reaction. The resulting whole-cell current due to opening of receptor-channels is recorded and analyzed. This technique is used in combination with a cell- flow technique with a 5-ms time resolution. This approach overcomes the limitations of previous techniques with inadequate time resolution that has hampered research in this area during the last 40 years and can be used with intact single cells, oocytes, and circuits of cells.